In papermaking operations a number of endless belts woven of synthetic yarns and filaments are used, including the initial forming fabrics, wet press felts and dryer felts. To obtain desirable results in the papermaking process several different characteristics of various weaves are sought. These characteristics include air permeability to assist in removing water from the papermaking slurry or furnish, dimensional stability, long wear and, for finer grades of paper, a relatively smooth supporting surface on the papermaking side of each fabric. In these papermaking fabrics, particularly with respect to the forming fabrics, a smooth upper or paper supporting surface is desirable to provide a smooth surface on the paper mat being formed. This characteristic can be obtained by providing a dense and tightly woven paper supporting surface, but such a tightly woven surface reduces the air permeability and thus water removal, requiring a slower running speed on the papermaking apparatus in order to remove the necessary amount of water. Looser and more open weaves can provide a more rapid removal of water, but provide less support and thus a rougher marking of the paper surface than the close weave.
It has been found that some of these desirable characteristics of greater support provided by a tighter weave may also be provided to a looser, more open weave, by the provision of additional, or extra support yarns extending in the cross machine direction and interwoven with the machine direction yarns. These extra support yarns may conveniently be provided in the form of an extra yarn interposed between each pair of the main cross directional yarns.
Use of such extra support yarns has been disclosed in prior patents, such as Kositzke, U.S. Pat. No. 4,909,284, which provides for such extra support yarn in a papermaking fabric. However, in Kositzke, as well as in other known papermaking fabric weaves utilizing extra support yarns, the full benefit of those extra support yarns may not be realized because of the multiple warp float extending over two or more of the cross machine direction yarns in each weave repeat. Such double or triple warp floats pull those cross machine direction yarns below the papermaking surface of the fabric and reduce the maximum length possible for support given by the cross direction yarns in each weave repeat. This inherently provides a rougher papermaking surface for the fabric and, thus, a less smooth paper manufactured thereby.